ESSENTIAL ROLE FOR GAMMA-TUBULIN IN THE ACENTRIOLAR FEMALE MEIOTIC SPINDLE OF DROSOPHILA

Microtubule nucleation in vivo requires gamma-tubulin, a highly conser ved component of microtubule-organizing centers. In Drosophila melanog aster there are two gamma-tubulin genes, gamma TUB23C and gamma TUB37C . Here we report the cytological and molecular characterization of the 37C isoform, By Western blotting, this protein can only be detected i n ovaries and embryos. Antibodies against this isoform predominantly l abel the centrosomes in embryos from early cleavage divisions until cy cle 15, but fail to reveal any particular localization of gamma-tubuli n in the developing egg chambers. The loss of function of this gene re sults in female sterility and has no effect on viability or male ferti lity. Early stages of oogenesis are unaffected by mutations in this ge ne, as judged both by morphological criteria and by localization of re porter genes, but the female meiotic spindle is extremely disrupted. N uclear proliferation within the eggs laid by mutant females is also im paired, We conclude that the expression of the 37C gamma-tubulin isofo rm of D. melanogaster is under strict developmental regulation and tha t the organization of the female meiotic spindle requires gamma-tubuli n.